In the energy
sources that we use every day all forms of energy are stored in
different ways. These sources are divided
into two groups renewable
(an
energy source that we can use over and over again) and nonrenewable
(an energy source that we are using up and cannot recreate in a
short period of time).

However, we get most of our energy from nonrenewable energy sources,
which include the fossil fuels -- oil,
natural gas, and coal. They're called
fossil fuels because they were formed over millions and millions
of years by the action of heat from the Earth's core and
pressure from rock and soil on the remains (or
"fossils") of dead plants and animals. Another
nonrenewable energy source is the element uranium
whose atoms we split (through a process called nuclear fission)
to create heat and ultimately electricity.